The present invention relates to a substrate processing method comprising applying a resist solution onto a large substrate such as a liquid crystal display (LCD) substrate and removing the coated resist from the peripheral edge portion of the substrate.
In a manufacturing process of the LCD substrate, a circuit pattern is formed on a glass substrate by a so-called photolithographic process. The photolithographic process including steps of drying a substrate, coating a resist solution on the substrate, exposing the coated resist film with a pattern, and developing the exposed resist film. In such a photolithographic process, it is important to maintain constant atmospheric temperatures of processing units. This is because quality of the coating resist film is strongly affected by the atmospheric temperature. For this reason, the substrate processing apparatus is placed in an air-conditioned clean room. Furthermore, the clean air of the air-conditioned clean room is introduced into the substrate processing apparatus, thereby adjusting processing temperature to a desired temperature (constant temperature) at the time the substrate is coated with a resist. In other words, the same clean air atmosphere as that of the clean room, whose temperature and humidity are controlled, is used as an inner atmosphere of the substrate processing apparatus. In this manner, the processing atmosphere in the coating unit for coating a resist on the substrate can be adjusted to the desired temperature (constant temperature). As a result, a resist film is formed in a film thickness controlled more accurately.
However, the atmosphere of the clean room varies depending upon various factors. Due to the influences of the various factors, the inner atmosphere (temperature and humidity) of the substrate processing apparatus changes. As a result, a resist film is formed in uneven thickness. In addition, the processing apparatus for the LCD substrate is large since the LCD substrate is larger than a semiconductor wafer. As a result, the atmosphere of the apparatus is not uniform in temperature and humidity. In other words, temperature and humidity of the atmosphere significantly differs depending upon sections of the apparatus. In particular, if the atmospheric temperature of the coating unit changes, the resultant resist film is formed in a thickness which deviates significantly from a desired value and formed in an extremely non-uniform thickness, producing a coating defect. Consequently, the yield of a final product tends to decrease.
The aforementioned temperature change of the atmosphere is one of reasons for the following phenomenon called "indirectly influenced mark". When a temperature change occurs between a contact member in contact with the substrate at its lower surface and the substrate when the substrate is processed or transported, the resist film formed on the upper surface of the substrate corresponding to the contact site by the contact member quantitatively and qualitatively differs from the resist film of the remainder portion.
In generally known methods, the photolithographic process is applied to a substrate horizontally fixed on a table or to a spinning substrate. In the case of the LCD substrate, the LCD substrate is adsorbed and held by a plurality of adsorption members provided on the upper surface of the table. More specifically, these adsorption members adsorb the rear surface of the substrate, thereby fixing the substrate on the table.
The table having adsorption members is used in a process of removing a coated resist from the peripheral edge surface of the substrate. In the process for removing a peripheral-edge resist, a solvent (e.g., thinner) is supplied to the peripheral edge portion of the substrate from a nozzle while moving the nozzle along the peripheral edge portion of the substrate adsorbed onto the table. In this case, the resist dissolved in the solvent is removed by vacuum-evacuation of the substrate peripheral edge portion. Note that the adsorption members keep adsorbing the rear surface of the substrate during the process.
In a conventionally-used apparatus, even if such a removal process is applied, the resist coating film formed on the upper surface of the substrate whose lower surface is adsorbed by the adsorption members differs in quantity and quality from that formed on the upper surface of the substrate whose rear surface is not adsorbed by the adsorption members. More specifically, marks are made on the surface of the substrate by indirect influence of the adsorption members attached on the rear surface (hereinafter referred to as "indirectly influenced mark"). The indirectly influenced mark of this type have a negative effect on the light-exposure processing and the developing performed in later steps. As a result, the yield of the final LCD product may decrease.